This is a non-randomized, open-label, multi-center efficacy and safety study in patients receiving a conventional six-week course of cranial radiation therapy for glioblastoma multiforme. To be eligible for entry into the study, patients must have a histologically confirmed suprtentorial grade IV astrocytoma (glioblastoma multiforme). The daily dose of RSR13 will be 100mg/kg at a concentration of 20mg/mL administered over 30 minutes via a central venous access device. RSR13 administration will begin on the first day of radiation therapy, occur every day of radiation therapy, and be timed so that the end of infusion occurs within 30 minutes of the start of radiation therapy. Patients will be assessed for safety, adverse events, and toxicities throughout dosing and radiation therapy and until progression of disease or death. The Radiation Therapy Oncology Group (RTOG) recursive partitioning analysis (RPA) for glioblastoma constitute the historical database to determine the sample size for this study. Screening and eligibility criteria will capture the prognostic factors which comprise the RPA strata for glioblastoma multiforme.